1. Field of the Invention
The present disclosure relates to a method of quantitatively analyzing uranium in an aqueous solution by using a ratio between Raman scattering intensity of water and luminescence intensity of uranium.
2. Description of the Related Art
Since ground water plays an important role in transport and redistribution of elements constituting the Earth's crust, there are many cases in which techniques for measuring environmental radioactive isotopes in ground water can be a useful means of geochemical and mineral exploration research. Most of radioactive isotopes in ground water are generated from actinide elements such as uranium and thorium that exist in nature. Uranium among natural radioactive elements particularly causes harm to health by being accumulated in bones and kidneys when ingested. With respect to uranium, chemical risk is greater than radioactivity. According to the evaluation by international commission on radiological protection (ICRP), it has been known that about 5% of ingested uranium is generally absorbed into blood stream through stomach. With respect to the foregoing risk of uranium, the U.S. environmental protection agency (EPA) was established maximum contamination levels (MCL) for environmental radioactive isotopes in public drinking water as the national interim primary drink water regulation (NIPDRW) in 1976.
Since uranium used as nuclear fuel exists in a trace amount in sea water, earth's surface, and environmental samples, an analysis method having a low detection limit has been required in order to quantitatively analyze uranium. In analysis methods of uranium reported to date, a titration method, absorption spectrometry using a spectrophotometer, fluorescence spectrometry using a fluorophotometer or a pulse laser light source, and chromatography have been widely used. However, the foregoing methods have limitations of a pretreatment process of a sample, matrix effects, prolonged analysis time, and requirements of expensive equipments and high costs.
U.S. Pat. No. 4,641,032 relates to a method of quantitatively analyzing a trace amount of uranium in a solution by using fluorometry. Luminescence of uranium molecules in the solution is generated by the incident of a pulsed laser beam. At this time, uranium luminescence signals decreased as an exponential function of time are recorded and initial intensities (I0) of uranium luminescence excluding laser pulse signals with respect to a uranium standard solution and an unknown uranium sample are measured. The method then quantitatively analyzes uranium by comparing the initial luminescence intensities thereof.
Korean Patent Application Laid-Open Publication No. 1994-0011945 relates to a nitrogen laser-induced uranium fluorescence analysis apparatus using optical fibers, in which a uranium concentration is quantitatively analyzed by measuring uranium luminescence emitted when a uranium aqueous solution is irradiated with a pulsed nitrogen laser beam. The foregoing analysis apparatus is characterized by that a nitrogen laser beam is incident on a sample-charged optrode by using optical fibers for laser beam transmission and generated luminescence signals are collected with optical fibers for luminescence transmission so as to be incident to an oscilloscope as a detector.
All the typical methods for quantitative analyzing uranium must obtain a calibration curve for measuring the concentration thereof by preparing standard samples having different concentrations in order to quantitatively analyze uranium in an unknown sample. Since the calibration curve may be different according to the intensity of a light source and the sensitivity of a detector, works for obtaining the calibration curve may be inconvenient because the works must be repeated whenever an unknown sample is measured.
Therefore, the present inventors developed a method of quantitatively analyzing uranium in an aqueous solution by using a ratio between Raman scattering intensity of water and uranium luminescence intensity, and confirmed that the foregoing method is effective in uranium analysis because the detection limit thereof is as low as that of a commercial analysis apparatus, thereby leading to completion of the present invention.